I don't think it is just a question of literacy (though I will always agree with the need for literacy for all). I feel it is also a question of early influences, conditioning if you like. As the Jesuits are supposed to have said-- Give us a child before the age of seven and we will have him (her) for life.

It takes a lot of conviction, as well as not a little courage to reject one's upbringing as in doing so we reject family, community and sometimes country. It is easier to cling to safe and comfortable beliefs, especially if the community is close, selective and promises exclusivity of rewards, perhaps even at the end of suffering for those beliefs. This can apply to something trivial, such as believing the planet was made in 6 days, as well as to the need for martyrdom for your faith. It's the same thinking and reasoning at work.